Japanese Fluvial Sculpin

Amphidromous. Refers to fishes that regularly migrate between freshwater and the sea (in both directions), but not for the purpose of breeding, as in anadromous and catadromous species. Sub-division of diadromous. Migrations should be cyclical and predictable and cover more than 100 km.Characteristic elements in amphidromy are: reproduction in fresh water, passage to sea by newly hatched larvae, a period of feeding and growing at sea usually a few months long, return to fresh water of well-grown juveniles, a further period of feeding and growing in fresh water, followed by reproduction there (Ref. 82692).

Bottom-dwelling fish of mountain streams.

The Japanese fluvial sculpin (Cottus pollux) is a species of freshwater ray-finned fish belonging to the family Cottidae, the typical sculpins. It is endemic to Japan, where it inhabits mountain streams in Honshu, Shikoku, and Kyushu. It reaches a maximum length of 15.0 cm (5.9 in) . It is also known as the Japanese bullhead.